1. INDUSTRIAL FIELD
The present invention relates to a disposable pressure transducer and a disposable pressure transducer apparatus which are used in the field of medicine and, more particularly, to a disposable pressure transducer and a desposable pressure transducer apparatus which are used for measuring the blood pressure of an organism, the inner pressure of the uterus, the innner pressure of the bladder, the pressure in the oesophagus, or other particular pressures.
2. PRIOR ART
In the order to cure a human being or an animal or to diagnose the physiological state thereof, a particular kind of pressure such as the blood pressure of the organism is measured. For example, in the case of measurement of the blood pressure of a human being, either an indirect measurement method or a direct measurement method is used to measure the blood pressure of a patient. In the former indirect measurement method which has heretofore been used, a pressure cuff and auscultation are utilized in combination, and a number of domestic sphygmomanometers have also recently been utilized. Such an indirect measurement method is advantageous in that neither pain nor burden is imposed on the patient, but it is disadvantageous in terms of the accuracy of measurement and continuity in monitoring. On the other hand, the direct measurement method is a method of measuring blood pressure by sticking an indwelling needle or a catheter into an artery of the arm of a patient and connecting an external pressure qauge by means of a liquid such as a Ringer solution. Although imposing pain on the patient, the direct measurement method has been more widely used than the indirect measurement method with respect to a patient who is being treated in an operating room or in an intensive care unit. This is because since blood pressure can be measured at the same time as execution of blood operations such as sampling of blood and injection of remedy, high-precision measurement of the blood pressure is realized and long-time continuous monitoring is enabled.
Sphygmomanometers of the type utilized in the direct measurement method are called "external pressure transducer apparatus". The development of the external pressure transducer apparatus has a long history and they have been used in a wide range of applications. Such an external pressure transducer apparatus previously employed a metal-foil strain gauge as a pressure-electricity conversion element. However, with the remarkable advances in semiconductor technology pressure transducer apparatus which utilizes semiconductor strain gauges have been used in the medical field. Such a semiconductor strain gauge is formed by preparing single-crystal silicon as a material and effecting thermal diffusion of impurities or ion implantation on a surface of the single-crystal substrate. Because of the high elasticity inherent in the material, the semiconductor strain gauge is commonly formed in the shape of a beam or a diaphragm.
The problem of infection with hepatitis or an AIDS virus has recently arisen and the reuse of a pressure transducer in blood-pressure measurement has come into question. To cope with these problems, semicondutor technology which can yield devices of miniature size, high accuracy and mass-producibility has been noticed and development of disposable pressure transducer (disposable sphygmomanometers) has been vigorously conducted.
A conventional type of disposable pressure transducer is described in Japanese Patent Laid-Open No. 197730/1987. This pressure transducer includes a sensor assembly in its housing, and the sensor assembly is produced by 1 bonding a sensor chip to a hermetically sealing disk, 2 bonding the hermetically sealing disk to an intermediate housing, 3 fixing an integrated circuit board to the intermediate housing, 4 connecting the sensor chip to electrical connecting terminals on the board, 5 bonding a cylindrical coupling lid to the intermediate housing, and 6 charging a pressure-transmitting medium into the interior of the coupling lid. Problems to Solved by the Invention
In order to realize a disposable pressure transducer, it is necessary to assure a lowe price because of its disposability and yet excellent operability and measurement performance. In order to realize the low price, it is necessary to reduce the number of parts to be used and also to enhance the efficiency of the assembly operation.
However, the above-described conventional disposable pressure transducer has the following problems.
a Both the intermediate housing of the hermetically sealing disk which surrounds the sensor chip and the inner space of the coupling lid because complicated due to, for example, the projection of a board coupling piece provided with the electrical connecting terminals. As a result, stagnant air easily accumulates during the step 6 of charging the pressure-transmitting medium, and the pressure transmission characteristics may deteriorate.
b Although the sensor assembly in itself may constitute the central portion for pressure conversion, the sensor assembly includes a large number of constituent parts such as the sensor chip, the hermetically sealing disk, the intermediate housing, the integrated circuit broad, the coupling lid and the like. This means that a large number of assembly steps are needed and that the aforesaid step 4 of electrically connecting (wire-bonding) the sensor chip and the board must be carried out in a narrow space within the intermediate housing; that is to say, the efficiency of the assembly operation is inferior.
c The flushing device, which serves to connect the pressure transducer to the external sterilized-liquid supply source, may be connected to the inlet side of the housing, or a three-way stop cock, which serves to alter the flow passage of a liquid, may be connected to the outlet side of the housing. In either case, however, the operation of connecting the flushing device or the three-way stop cock, hence a certain connection length, is needed. This means that the burden imposed on medical workers is increased and that the dynamic response of pressure sensing in made to fall, which hinders the accuracy of pressure measurement.
It is an object of the present invention to provide a disposable pressure transducer in which, although a sensor assembly in itself constitutes the central portion for pressure conversion, the construction of the sensor assembly is simple and pressure transmission characteristics are improved, and in which the number of constituent parts of the sensor assembly is small and the assembly process, hence the assembly operation, is simple, and which can be safely handled and is excellent in measurement performance.
It is another object of the present invention to provide a disposable pressure transducer apparatus of the type which is used with its pressure transducer connected to an external sterilized-liquid supply source or with its three-way stop cock for altering the flow passage of a liquid connected to the outlet side of a housing, which apparatus makes it possible to improve the accuracy of pressure measurement and to reduce the burden imposed on medical workers and which is safe and has excellent measurement performance.